Resins having a high softening point or a high SP value are generally used in racing tires and other similar tires to provide them with high grip performance during running, i.e. in high temperature conditions. However, when they are incorporated in large quantities, the hardness (Hs) at ambient temperature increases, with the result that the conformity to road surface irregularities decreases during the initial phase of the race, and thus the grip performance during the initial phase of running deteriorates.
It has also been proposed to add low temperature plasticizers such as TOP (a phosphoric acid ester) to ensure initial grip performance. In the case of diene rubber compounds such as compounds for treads, however, as the temperature increases, TOP bleeds to the rubber surface, resulting in a decrease in grip performance. This method also disadvantageously causes a deterioration in abrasion resistance.
Thus, there is a need for rubber compositions that provide good grip performance during the initial to middle and even to late phases of running while simultaneously ensuring excellent abrasion resistance.